Good work there BSA, bravo - My Dad, uncle, cousins and numerous mates have, Dad used to do the TT Course walk as well, my old bust up ankles can just about manage Douglas promenade. You'll need a good back up crew for motivation and supplies, shoes that you've worn in well and know are a must, when you think you can't go on any further - YOU CAN, I spent a couple of hours with a mate on the phone early morning coming up out of Ramsey one year, other hills like the Sloc are a killer but look ahead in little target segments not at the very top, you won't see your physical "wall" coming just be prepared to take care and listen to you body when it slows down a little. Hydration is critical without sounding obvious but it's easy to miss where you should be having a drink but very hard to get your body's levels back to where they should be - drinking 2 pints of fluid because you've missed one pint earlier isn't the answer. Best of luck, see if you can tag onto somebody else at your pace - it's a great motivation with a co-walker with you.